The detection of underground pipes and utility lines is a necessity when any construction work involving digging trenches is necessary. Many types of service lines such as telephone and telegraph cables, gas and sewer lines, electrical lines and water mains are located below the surface. It has become increasingly popular to utilize plastic pipe or plastic wrapped cables in this service. Also, ceramic and other nonmetallic materials such as concrete are used in underground service. The precise location of the nonmetallic lines cannot be determined by the metal detectors above ground used to locate metal pipe.
The problem of detection of non-metallic pipes has been addressed in several patents. In U.S. Pat. No. 3,115,861 a frangible colored body is laid underground over the buried service line. The colored body has a water insoluble color and has the benefit of being visible when contacted with solid during digging operations to warn the operator of the proximity of a service line. In U.S. Pat. No. 3,282,057 the use of a colored plastic tape laid over a service line when it was installed was disclosed. The plastic tape is colored and when it is pulled up by a digger, it provides a warning of the proximity of a buried line.
In U.S. Pat. No. 3,504,503 a method was disclosed for locating underground lines of the construction discussed herein which included using a metallic foil with a moisture and soil resistant coating and a coloring to distinguish from the soil. The colored foil frangible body is laid over the service line. The benefit of the foil is that metal detectors can be used to locate the foil and thereby the location of the service line.
In U.S. Pat. No. 3,633,533, a method to locate underground service lines is disclosed using a metal film coated with a colored plastic. The plastic is moisture and soil resistant. In an alternative embodiment a metallic wire is under the plastic coating. The plastic coated foil tape is used quite extensively. There are color codes for water, gas, electric, buried telephone and telegraph lines and other services. The tapes are printed with a cautionary message corresponding to the type of service line underlying the tape. U.S. Pat. 4,623,282 further discloses coloring of warning tapes.
U.S. Pat. No. 4,699,838, discloses a reinforced polymer tape. The tape is strong and has good handling characteristics.
The use of polymeric or plastic tapes has generally been confined to detection of service lines. The tapes have not been used in the area of prevention of tree root damage and other biological damage to service lines.